The present disclosure relates to solid-phase extraction. Specifically, the present disclosure relates to the use of expanded polytetrafluoroethylene (ePTFE) tubing as a stationary phase of a solid-phase extraction system.
The ability to extract a targeted analyte from a material has proven to be of great assistance in a variety of applications. For instance, the ability to assay the contents of test samples by targeted extraction of a specific constituent or constituents from a sample material has proven extremely useful in the testing and examination of biological and environmental samples. Similarly, chemical separation schemes often require the separation of one or more target constituents from a fluid to yield a desired purified product. For example, a short-lived radionuclide or radionuclides present together as decay progeny may be separated from the respective parent radionuclide(s) to permit use as an analytical standard, in a radiopharmaceutical, or as a component in a subsequent process. Often, when the constituent or constituents are not present in a physical or chemical state amenable to chemical separation, extensive physical or chemical preparation may be required prior to the chemical separation or final use. The preparation steps may include different combinations of physical processes, such as physical size reduction or filtering of particulates from a fluid, and chemical processes such as combustion or ignition, dissolution of a solid, or reaction with various chemical reagents to obtain a fluid containing the target constituents in physical and chemical forms that are amenable to the separation to be performed.
The ability to purify one constituent of a material by selectively removing unwanted components from a fluid also has an abundance of useful applications in the testing and examination of biological and environmental samples and in other more general settings. For example, radioanalytical separation schemes may require removal of interfering constituents in a solution to yield a desired purified product. Similarly, parent radionuclides may need to be separated from short-lived decay progeny to allow the use of progeny species as analytical standards, in radiopharmaceuticals, or as input materials for a second process. Often, when the constituent or constituents are not present in a physical or chemical state amenable to chemical separation, extensive physical or chemical preparation may be required prior to the chemical separation or final use. The preparation steps may include different combinations of physical processes, such as physical size reduction or filtering of particulates from a fluid, and chemical processes such as combustion or ignition, dissolution of a solid, or reaction with various chemical reagents to obtain a fluid containing the target constituents in physical and chemical forms that are amenable to the separation to be performed.
Traditional solid-phase extraction systems utilize a stationary phase of resins or fibers to separate a targeted set of analytes or constituents from a fluid sample. The resins or fibers of these systems contain a binding agent having an affinity for the targeted constituents. The resins or fibers are then packed into an outer sleeve, such as a column or micropipette tip.
Several problems exist with traditional extraction systems. For example, one important limitation of traditional solid-phase extraction systems is that the stationary phase must remain surrounded in liquid to prevent air gaps and fissures in the packed resins or fibers from disrupting the functionality of the extraction system. Additionally, the process of packing the resins or beads is often a time consuming, delicate procedure involving multiple steps. Furthermore, some traditional systems require long equilibration periods or high pressures to move a sample through the stationary phase. Finally, the complexities and encumbering processes of traditional solid-phase extraction systems are costly both in time and resources thereby confining the use of the systems to a well-equipped laboratory.
What is needed in the art is an improved stationary phase and solid-phase extraction system that is both useful in a laboratory setting as well as transportable and efficient in extracting or purifying one or more targeted constituents and that is amenable to use with a wide range of extractants. Additionally, a stationary phase is needed that does not require constant immersion in a liquid and that does not require lengthy equilibration periods or high pressures to operate.